One aspect of plasma membrane structure which has gained much attention over the last three years is the mobility of both the lipid and protein components in the lateral plane of the surface membrane. The use of plant agglutinins (Lectins) has permitted a phenomenologically directed analysis of the mechanism(s) whereby the relative degree of mobility of specific surface glycopeptides is controlled. We are using a series of sub-clones derived from Chinese hamster ovary cells to study the regulation of the lateral mobility of lectin receptors. These CHO sub-clones are well suited for this study since they respond rapidly in terms of both morphology and surface architecture to growth in medium containing dibutyryl cAMP. Specifically we are testing a model which suggests that lectin receptor mobility in these CHO sub-clones is dependent on the degree of association of the lectin receptors with a hypothetical stationary peptide complex which, in turn, is held in a fixed mode via an association with intracellular microtubules and microfilaments. We are currently investigating the role of membrane peptide plasphorylation in controlling lectin receptor mobility and are emphasizing the use of lectin affinity chromatography for isolating and characterizing surface receptor complexes. BIBLIOGRAPHIC REFERENCES: An Analysis of Lectin-Initiated Cell Agglutination in a Series of CHO Subclones which Respond Morphologically to Growth in Dibutyryl Cyclic AMP. j. van Veen, R.M. Roberts and K.D. Noonan. J. Cell Biol. 70: 204 (1976). The Relationship of Membrane Glycopeptide Composition to Losses in Concanavalin A Agglutinability Induced by Dibutyryl Cyclic AMP in Chinese Hamster Ovary Cells. J. van Veen, K.D. Noonan and R.M. Roberts. Exp. Cell Res. 103:405 (1976).